This invention relates to cargo barrier nets. More particularly, this invention relates to cargo barrier nets that are used to restrain cargo that is being transported by an aircraft.
Cargo barrier nets are used to restrain cargo that is being transported by an aircraft. The cargo barrier net is positioned between the occupants of the aircraft and the cargo. The cargo is generally located in an aft portion of the aircraft. The purpose of the cargo barrier net is to protect the occupants who are located in a forward position relative to the cargo barrier net. The configuration of the cargo barrier net determines the magnitude and direction of loads that are placed on an airframe structure of the aircraft when the cargo barrier net restrains the cargo. The configuration of the cargo barrier net also determines a net displacement length of the airframe set aside that is for displacement of the cargo barrier net.
As can be appreciated, the airframe space that is set aside for the net displacement length cannot be used for cargo, passengers and/or equipment. In an effort to increase the amount of payload that can be carried by the aircraft, aircraft manufacturers have decreased the net displacement length. Cargo barrier nets have been redesigned to accommodate the same loads that occur during a crash with a shorter net displacement length. These designs, however, place higher loads on the airframe structure than it is capable of handling. One possible solution is to increase the capacity of the airframe structure in the areas where the cargo barrier net is connected to the airframe structure. Increasing the strength of the airframe structure, however, increases the weight and cost of the aircraft.
Conventional barrier nets have a spider web configuration or a rectangular mesh configuration. When designing a cargo barrier net, simplifying assumptions have been used to establish the shape of the cargo barrier net under load for a particular configuration. Loads imposed on the airframe structure of the aircraft and the net displacement length of the cargo barrier net have been derived from the shape of the cargo barrier net. When shorter net displacement lengths are desired, conventional cargo barrier nets are unable to provide interface loads that are within the structural capability of the airframe structure of the aircraft. A limiting factor has also been the ability to analyze changes to configurations of the cargo barrier net and their impact on the loading of the airframe structure. Therefore, there is a tendency to over-design the cargo barrier net.
A cargo net for an aircraft according to the invention includes a central ring. A plurality of radially projecting webs include a radially inner end that is connected to the central ring. A radially outer end of the radially projecting webs is connected to the airframe. A first circumferential web is connected to a first set of mid-portions of the radially projecting webs. The first set of mid-portions is located radially outside of the central ring. The second circumferential web is located radially outside of the first circumferential web. The second circumferential web is connected to a second set of mid-portions of the radially projected webs. The second set of mid-portions is located radially outside of the first set of mid-portions.
In another feature of the invention, a third circumferential web is located radially outside of the second circumferential web. The third circumferential web is connected to a third set of mid-portions of the radially projecting webs. The third set of mid-portions is located radially outside of the second set of mid-portions. The third circumferential web is connected to less than all of the radially projecting webs.
In still another feature of the invention, a fourth circumferential web is located radially outside of the third circumferential web. The fourth circumferential web is connected to a fourth set of mid-portions of the radially projecting webs. The fourth set of mid-portions is located radially outside of the third set of mid-portions. The fourth circumferential web is connected to less than all of the radially projecting webs.
In still other features of the invention, the radially projecting webs are connected to the first, second, third and fourth circumferential webs using stitches.
In yet another feature of the invention, the radially projecting webs include a shunt that releases under load to allow the radially projecting webs to lengthen.